Gotta admit, that's an interesting photo. No telling how many sea creatures that we have no idea even exists. We still have a lot of unexplored ocean. But why they would call it a "sea monster" is plain retarded. Why not just call it "strange creature" or "strange species". It would give it more credibility.

For once, something in the water ain't paredolia. I like the beaked whale answer, but would be happier if there was any sense of scale. Maybe the reason it looks "mythological" is because it's a direct inspiration for several aquatic mythological creatures. This is a really cool picture, but doesn't need to be described as an all-caps SEA MONSTER.

Yet, if one goes and does 15 minutes of online research, you find that you can eliminate 95% of possibiliities, and once you have your choices down to one, the answer can only be that it is X, or it new creature Y. So then what are the chances of a brand new species of dolphin/whale living in the waters off of Greece? Maybe one in a million? Where are the rest of them, then? There has to be a breeding population, right? At least a couple dozen... yet we only have the one photo. Or... we can see from the deion of a beaked whale that their appearance is highly variable.